Novel benzo[c][1,2,5]oxadiazole-naphthalenediimide based copolymer for high-performance air-stable n-type field-effect transistors exhibiting high electron mobility of 2.43 cm2 V−1 s−1

Abstract

A strongly electron-withdrawing benzo[c][1,2,5]oxadiazole (BOZ) unit, as the second electron acceptor segment, is incorporated into the naphthalenediimide (NDI) based polymer backbone for the first time. Therefore, a unipolar n-type polymer semiconductor (PNBO) with a regioregular A1–D–A2–D configuration is developed successfully. It is found that BOZ-containing polymer PNBO not only has a deep-lying LUMO energy level of ca. −4.0 eV, which facilitates electron-injection from an Au electrode into the active layer, but also possesses a deep enough low HOMO energy level of −5.9 eV for blocking hole-injection. The carrier transporting performance of PNBO is characterized by solution-processable polymeric field-effect transistors (PFETs). These results demonstrate that a smooth surface morphology and a compact solid stacking endow PNBO with excellent unipolar n-type electron-transporting characteristics; a highest electron mobility of up to 2.43 cm² V⁻¹ and an excellent shelf storage with a negligible decay in 70 days are achieved.